I've been hearing mixed things about these 4-day work weeks. It was proposed here in Belgium by the PS (socialist party), but an expert in labour economics said that it's absolutely unrealistic (unless people are willing to get lower wages and consume less). According to him, the academic world is almost unanimously opposed to it. He says that on the long term there would be a disastorous rise in wage costs and unemployment, because employers will either try to automate more or move to other countries. He also says that the number of burn-outs might stay the same anyways.